From what we hear, American girls are among the most ­privileged and successful girls in the world.

But tell that to a 13-year-old who gets called a slut and feels she can’t walk into a school classroom because everybody will be staring at her, texting about her on their phones. Why are they complicit in this potentially very self-­undermining aspect of social­media culture? Everything’s about the likes.” If building a social-media presence is similar to building a brand, then it makes a twisted kind of sense that girls—­exposed from the earliest age to sexualized images, and encouraged by their parents’ own obsession with self-promotion—are promoting their online selves with sex.

But while we’re consumed by the tangible dangers of messenging services like Kik, Yik Yak, After School and other anonymous apps, we may be missing a different influence: our own behavior.

Kids today are often accused of being narcissistic, but they may be learning their exhibitionist ways from their parents.

I spent the past 2½ years researching my new book American Girls: Social Media and the Secret Lives of Teen­agers, visiting 10 states and talking to more than 200 girls.